Radio receiving apparatus



Jan. 6, 1942.

J. R. REID ,RADIO RECEIVING APPARATUS 11 Sheets-Sheet 1 INVENTOR. j mm ESLM BY ATTORNEY.

Filed Jan. 8, 1958 Jan. 6, 1942. J. R. REID 2,268,619

RADIO REEIVING APPARATUS Filed Jan. 8, 1958 ll Sheets-Sheet 2 ITEM 5 I725 fi".

IN V EN TOR.

U ZTTORNEY v Jan.

J. R. REID RADIO RECEIVING APPARATUS Filed Jan. 8, 1938 ll Sheets-Sheet 3 INVENTOR. xii/man $1,

Jan. 6, 1942. J R REID RADIO RECEIVING APPARATUS "1 :lllll J [llllllll J Jan. 6, 1942. J. R. REID RADIO RECEIVING APPARATUS Filed Jan.

8, 1938 ll Sheets-Sheet 5 ATTORNEY iwm Jan. 6, 1942. J. R. REID RADIO RECEIVING APPARATUS 11 Sheets-$heet 6 17 IRE-.16

Filed Jan. 8, 1938 INVENTOR. Jam/a a. 3410 BY ATTORNEY Jan. 6, 1942.

J R. REID RADIO RECEIVING APPARATUS 11 Sheets-Sheet 7 INVENTOR. Jam 51.3w

I I Y El ATTORNEY Jan. 6, 1942, J. R. REID RADIO RECEIVING APPARATUS Filed Jan. 8, 1958 ll Sheets-Sheet 9 INVENTOR. Jam 51 @144) BY dfli,

ATTORNEY 7 Jan. 6, 1942. J. R. REID RADIO RECEIVING APPARATUS Filed Jan. 8, 193a 11 Sheets-Sheet 11 A TTORNEY Patented Jan. 6, 1942 UNITED STATES PATENT OFFICE RADIO RECEIVING APPARATUS Application January 8, 1938, Serial No. 184,062

8 Claims.

My invention relates broadly to radio receiving apparatus and more particularly to an improved construction and method of assembly for a radio receiving apparatus.

One of the objects of my invention is to provide an improved construction of radio receiving apparatus having a high electrical efliciency resulting from the substantial elimination of interconnecting buses or lead wires in the chassis of the receiver.

Another object of my invention is to provide a simplified construction of radio receiving apparatus in which the parts of the receiver are so assembled as to be readily accessible for repair and replacement.

Another object of my invention is to provide a construction of radio receiving apparatus which is inexpensive in manufacture and production and which is readily adaptable for standardization in the industry to allow compact assembly and distribution of radio receiving apparatus.

A further object of my invention is to provide a construction of radio receiving apparatus in which improved units may be substituted for obsolete units from time to time for maintaining the apparatus modern in all respects and capable of including the improvements in the art without the necessity of abandoning the original receiver.

A further object of my invention is to provide a construction of radio receiving apparatus which embodies a heart adapted to provide removable interconnection for separable units constituting the radio receiving apparatus for establishing extremely short interconnections between parts of the units for substantially reducing the losses and improving the electrical efficiency oi the apparatus.

Still another object of my invention is to provide a construction of radio receiving apparatus having a centralized interconnection member with respect to which removable compact units may be readily assembled and electrically interconnected for completing the circuits of the radio receiving apparatus, tuning equipment and sound reproducing system, with minimum interconnecting leads or buses.

A further object of my invention is to provide a construction of radio receiving apparatus adapted to be assembled by means of coacting compact replaceable units in which selected units are provided with electrical indicators energizable from the normal operating current used for excitation of the respective units for indicating the operative condition of the units so that upon failure of the electrical indicator in any one of the units, such unit may be readily removed and replaced, allowing for quick and inexpensive servicing of the apparatus.

Still another object of my invention is to provide a construction of radio receiving apparatus composed of and constituted by a number of coacting replaceable units assembled in such manner that failure of any one of the units may be readily localized and the apparatus serviced and repaired and replacements made at minimum cost and with minimum expenditure of time.

Still another object of my invention is to provide a construction of electron tube apparatus constituted by a multiplicity of coacting replaceable units in certain of which protective devices are included for substantially eliminating the effect of destructive currents upon the elements of the unit in the event of emergency or abnormal conditions for the protection of the parts of the unit and coacting parts of related units.

A further object of my invention is to provide protective means for the power supply circuits and related parts therein of a radio receiver such as the windings of the power transformer, condensers and reactors of the main filter circuit and the field of the electrodynamic sound reproducer generally employed in the sound reproducer circuit of a radio receiving apparatus.

A still further object of my invention is to provide a radio receiving system constituted by a multiplicity of coacting replaceable units having electron tube circuits therein and in which selected electron tube circuits have the elements thereof protected by means of electrical fuses and visual indicators which also serve in coaction with resistor elements in the electron tube circuits for deriving the proper bias and voltage potentials for the correct operation of the tube circuits.

A further object of my invention is to provide a system of replaceable units for assembling a radio receiving apparatus in which individual elements constituting the replaceable units are also readily replaceable for facilitating servicing and repair of the individual units.

Other and further objects of my invention reside in the construction of heart, replaceable units, indicators, chassis and the assembly of the replaceable units with respect thereto as will be set forth more fully in the specification hereinafter following by reference to the accompanying drawings in which:

Figure 1 is a schematic wiring diagram of the K radio receiver system of my invention; Fig. 2

is a plan View of the radio receiver of my invention; Fig. 3 is a side elevational view looking in the direction of arrow A in Fig. 2; Fig. 4 is a sideelevational view looking in thedirect-ion ofarrow B in Fig. 2; Fig. 5 is a perspective view ofthe heart of the radio receiver constituting my invention; Fig. 6 is a schematic view of one form of tuning unit which may be employed in the system of my invention; Fig. 7 is a view of a, differ.-

en form of tuning unit which I may employ in the system of my invention; Fig. Bis a plan view of the chassis for the first detector unit; Fig. 9 is a schematic circuit diagram of the apparatus carried on the chassis shown in Fig. 8; Fig. 10

is a schematic view of the condenser-resistor arrangement of the apparatus shown in Fig. 8; Fig. 11 is a longitudinal sectional View through the first detector unit; Fig. 12 is a transverse secv tional View through the first detector unit; Fig. 13,

is a plan view of the first intermediate frequency unit; Fig. 14 schematically shows the arrangement of the condensereresistor units on the chassis illustrated in Fig. 13; Fig. 15 is a schematic circuit diagram of the, equipment carried by the chassis illustrated in Fig. 13; Fig. 16 is an end elevational view of the second intermediate frequency amplifier unit; Fig. 17 is a longitudinal sectional view through the second intermediate frequency amplifier unit; Fig. 18 is a bottom plan view of the second intermediate frequency amplifier unit; Fig. 19 is. atransverse sectional View taken on line l9l9 of Fig. 18; Fig. 20 is a plan View of the chassis of the second intermediate frequency amplifier unit; Fig. 21 shows the arrangement of the condenser-resistor elements on the chassis of the second intermediate frequency amplifier unit; Fig. 22 shows a circuit arrangement'of the equipment carried by the chassis illustrated in Fig. 20; Fig. 23 is a plan view of the chassis of the second detector unit; Fig. 24 shows the arrangement of the condenser-resistor combination employed on the second detector unit; Fig. 25 is a schematic circuit arrangement of the elements carried by. the chassis illustrated in Fig. 22; Fig. 26 isv a plan view of the chassis of the first audio frequency amplifier unit; Fig. 27 shows the arrangement of the condenser-resistor units carried by the chassis illustrated in Fig. 26; Fig. 28 is a schematic circuit arrangement of the equipment carried by the first audio frequency amplifier stage illustrated in Fig. 26; Fig. 29 shows, in plan.

view, a preferred. form ofv chassis for the second audio frequency amplifier stage; Fig, 30 illustrates the condenser and resistor arrangement for the elements carried by the chassis shown in Fig. 29; Fig. 31 shows a circuit arrangement of the elements carried by the chassis shown in Fig. 29; Fig. 32 is a plan view of the modified form of second audio frequency amplifier stage; Fig. 33 shows the schematic arrangement of the condenser-resistor units carried by the chassis illustrated in Fig. 32; Fig. 34 illustrates the circuit arrangement of the equipment carried by the chassis illustrated in Fig. 32; Fig. 35 is a side elevational view of one form of sound reproducer embodying my invention; Fig. 36 is an elevational view of the sound reproducer shown in Fig. 35;

Fig. 37 is an elevational view showing the detachable arrangement of the input transformer; the sound reproducer and the mounting for the sound reproducer; Fig. 38 is a view showing a modified method of mounting the sound reproducer of my invention; Fig. 39 is a plan view of the chassis of one form of rectifier and filter unit employedin the system of my invention; Fig. 40 shows the circuit arrangement of the rectifier andv filterunit; illustrated in Fig. 39; Fig. 41 is an elevational view of the replaceable condenser unit employed in the rectifier and filter unit of Fig. 39; Fig. 42' is a plan view of the condenser unit shown in Fig. 41; Fig. 43 shows a modified form of chassis for mounting the modified arrangement of rectifier and filter unit employed in myinvention; Fig. 44 is aside elevational View of a form of carton mounting for the condenser unit employed in the chassis illustratedin Fig. 43;

Fig. 45 is an end view of the condenser unit illustrated in Fig. 44; Fig. 46 is a perspective view of the power transformeremployed in. the system of my invention; Fig. 47 is a-top plan view partially broken away showing a carton unit for the condenser-resistor elements employed in certain of the units of the equipment of my invention; Fig. 48 is a transverse section on line l348 of Fig. 47; Fig. 49 is a transverse sectionon line 4949 of Fig. 47.; Fig. 50 is a detail of one method of mounting and establishing electrical connection with the condenser-resistor units; Fig. 51 is a longitudinal cross sectional view-throughthe cartontaken on line 5!-5l of Fig. 47; Fig. 52-

is a bottom plan viewof the carton unit; Fig. 53-- is a-view illustrating a modified arrangement of condenser or resistor mounting having-recesses in the end caps on the units; and Fig. 54 isa detailed sectional. view showing the manner of mounting a condenser or resistor unit'with are cess in the end cap thereon in lieu of a rounded protuberance of the form illustrated in Fig. 50.

My invention is directedbroadlyto a construction of radio receiver adapted for both television and sound broadcast reception in'whichthe construction of the receiver is greatly simplified to permit quantity production at relatively low; cost. The receiver of my invention is characterized by extreme simplicity and compactness and high electrical efficiency. The construction of the receiver of my inventiondeparts widely from radioreceiver construction hereto? fore known as I provide an arrangement whereby various coacting units constituting the radio. receiver may be removably. interconnected through a heart which substantially reduces the length of interconnecting busses or leads and eliminates the customary-wiring in the chassis of the usual type of radio receiver as heretofore known. 'Ihe'radioreceiver of my invention may embody a'varietyof electrical circuits. andthe.

W circuit I have-selected, forillustration of myinvention herein is not to be regarded in the limiting sense but is to be considered only as explanatory of my invention and as illustrating one form of circuit to which my invention is adapted. The circuit illustrated includes a tuning unit, a unit comprising an oscillator, a radio frequency amplifier and a mixer tube circuit, one or more units comprising intermediate frequency amplifier circuits, a unit comprising a sound detector circuit, which also provides for automatic volume control of the system, a unit comprising the first audio frequency amplifier stage, and a unit comprising the second audio frequency amplifier stage, a separable electrodynamic' sound reproducer unit and a replaceable rectifier and filter unit, and a replaceable power transformer. I have termed the means by which the several coacting units constituting the radio receiver of my invention are assembled as the heart.

The assembly of the apparatus of my invention may be described as comprising:

1. Main chassis:

a. Chassis envelope b. Heart 2. Units:

a. Chassis heart b. Plugs or sockets 3. Parts:

a. Secured to the main chassis b. Secured to the heart 0. Secured to the unit For convenience I have described the parts noted above as follows:

1. (a) The main chassis is composed of a base and vertical metal envelope in which apertures are cut for access to connections.

(b) The heart is composed of insulation plates between and on which are placed conductive plates and straps having plugs or sockets. These plugs or sockets extend outward to both sides of the heart so as to facilitate connections from the outside.

2. (a) The units are composed of insulation plates between and on which are placed conductive plates which make proper electrical connections between the various parts of the circuit.

(b) The units are designed to have plugs or sockets to facilitate the connection into the chassis heart (l-b) through the apertures in the chassis envelope (l-a) thereby making proper electrical connections which complete the circuit or circuits for which it is designed.

3. (a) Parts of the apparatus such as the electro-dynamic speaker, tuning unit, etc., can be held to the main chassis by securing means such as plugs and sockets.

(0) Parts of the radio such as the resistors and condensers are held in their proper position within the units by clips.

The use of the heart referred to above permits electrical connection to be established between coacting parts of the receiver with a minimum length of electrically conductive path between the parts, thereby increasing conductivity of the paths extending between the parts with the resulting increase in electrical efiiciency of the apparatus and allowing minimum distributed capacity and induction between interconnecting conductors, a reduction in feed back, interaction, local interference and other undesirable effects incident to the Wiring in the chassis of the usual type of radio receiver. By use of the heart consisting of a few small plates and metallic tubes with which the parts and the units are closely aligned, a great mass of interlocking or intermingling and complicated wires and soldered connections are dispensed with, thereby reducing the manufacturing cost to a minimum while increasing the electrical efilciency and compactness thereof. The fact that the several units constituting the radio receiver are independently removable and replaceable permits the modernizing of the radio receiver from time to time by substitution of an improved unit for an obsolete unit. This is particularly desirable at the present state of the art with respect to television receivers.

In order to set forth the special advantages arising out of the manufacture and use of the radio receiver of my invention, I have summarized the advantages as follows:

Accessibility 1. Main chassis:

a. Heart connections, electrical and securing meansThe heart that connects up the various circuits in the units makes possible the accessibility to the units and their parts.

2. Units:

a. Electrical connectors and securing means-Every unit having its own electrical connecting and securing means makes possible the quick removal and access to all of its parts.

b. Ease of construction on fiat surface Each unit has an open bottom, making quick repair possible.

c. Parts removably connected to unit-All small parts connected to the units such as resistors and condensers can be quickly removed due to each having its own electrical and securing means.

3. Parts removably connected to main chassisare accessible and quickly detachable because each has its own electrical connections and holding meansviz: speaker and tuning unit:

a. Parts removably connected to heartsuch as viz:Wave band switch, power transformer, etc. are accessible and quickly removable and replaceable because each has its own electrical and securing means.

parts saves many feet of complicated wiring and soldered connections.

b. Units-Units arev constructedof so few parts and constructing'material that they are'very simple to assemble and connect up.

; Parts-Such as transformers, speaker,

condensers etc., are'very easily attached or removed because each has its own electrical connections and holding. meansthereby requiring no soldering or bolting or long connectors.

2. Design:

a; Few partsDue to simplicity of: de-

sign; fewer and less complicated parts. are used.

b1. Consolidation of partsThe units and other largeparts are so compactly arranged, on.the main chassis, that comparatively avery small space is required.

c. Parts marked for identification and position in. the' units to. make replacement simple and quick.

d: Units and parts are not interchangeable withv each other on the main chassis: due to the position of' the connectors.

Standardization.

1. Parts:

a; Standard.- connections are used to facilitate. quick replacements.

b. Standard. sizes and shapes to facilitate ready replacements.

c. Replacements of obsolete parts can be made for. substitution of improved or modern parts.

2. Chassis is standardized. so that new. improvements in unitsand parts-canbeutilized.

a.. All large parts-and small parts as well as thosecontained in units are standardized so that improvements can be easily adapted.

b: Chassis and all parts are standardized so that new circuits can" be immediately installed.

Cheapness of manufacture 1. Chassis:

a. ConstructionThe chassis can be stamped out, both the conductor and insulation plates byv machines. The tubes or plugs can also be attached to conductive plates automatically. The chassis envelopeis readily made by, machine. To. put together the few parts that: complete a chassis is arsimple matter of assembly only.

b. Simplicity-It is easy to seez-the simplicity of this chassis in comparison to they complicated wired. chassis of other radio sets.

2. Units? a. Construction The units can be manufactured cheaply by machine as the insulation plates and conductors can be stamped out and quickly assembled.

b. Simplicity-The units. are simple in construction as there; arefew parts and easily'assembled;

Adaptability 1. Toapparatus using" electron emission tubes:

a5 Television systems. 17. Telephone repeaters, etc. 0. Radio broadcast receivers. cl. Automobile receivers-s e; Radio transmitters.

2. Additional circuits in unit form may be added when increase in power of the radio is desired; This is. accomplished by utilizing twin units or a double heart. An oversized chassis. may contain the double heart which willallow the use of'additional units.

Repairability.

l. Detachable parts:

Each part large and small contains. its own electrical connections and holding means by which elements are quickly and easily detachable. The parts are clearly marked and quick substitution by inexperienced persons is very simple.

2. Compactness:

Due to the arrangement of the various parts and units on the chassis and the small area occupied by the heart to which they are connected, the complete set is very compact. The units themselves being. very small in size and simple, add greatly to the complete compactness of the apparatus.

Centralization:

Centralization of the units and large parts around the connecting heart make extremely short connections between themselves possible. Centralizing the parts and units makes possible the use of a few conductor plates in the place of many feet of intermingled wires.

Eliminationof wires:

By-using a' heart as. constructed of a very few small conductor plates and units containing a minimum of conductor plates, there is marked improvement in electrical efiiciency and a substantial reduction in induction, local interference, of sapping of circuits, high resistance connection, of distributed capacity and induction, feed back, interaction, etc. By the use of a heart consisting of'a few small plates to which the parts and units are closely aligned; a great mass of interlocking intermingling and complicated wires and. soldered connections are dispensed with, thereby cutting the manufacturing cost to a minimum as well as increasing theefiiciency of the radio.

Indication of trouble, localization of same,

protection of parts:

By using indicators in the various circuits it is possible to acquire a comprehensive condition of the various parts of the set and which by being permanently connected in the circuit, immediately discloses and localizes a defective or weak part or tube, which can be immediately replaced thereby keeping the efiiciency ofthe radio at a maximum.

Referring to the drawings in more detail, I have illustrated my invention applied to a superheterodyne type of radio broadcast receiver although it will be understood that various circuit arrangements may be employed and details are immaterial. I have indicated the tuning unit of my invention generally by reference character I' connected through selectively tuned circuits 2 to the antenna system 3 and the ground system 4. The first of the sectionalized units includes the first detector oscillator and amplifier tube indicated generally at 5. The tube includes a heater element 5a and a cathode 5b. Adjacent the cathode 51), there is provided the oscillator grid Go. The anode grid Ga is located adjacent the oscillator grid Go. The screen grid Gs is connected as indicated. The control grid is indicated at G and the anode is shown at P. I provide in the cathode circuit leading from cathode 5b, the indicator and safety fuse A disposed in series with bias resistor R1 which connects to the ground lead 6. It will be observed that condenser C1 'is connected in shunt with the safety indicator A and resistor R1 for by-passing high frequency currents. The circuit from the oscillator grid Go extends through selected windings of the group of inductances indicated at I and through voltage limiting resistor R3 through safety indicator C to the high potential supply lead 8 indicated at B+. Resistor R3 is by-passed to ground by condenser Ca. In circuit with the screen grid Gs, I provide voltage limiting resistor R2 and safety indicator lamp B. The resistor R2 is by-passed by means of condenser C2. The indicator lamp B is by-passed by means of condenser C4. The indicator lamp B is connected in series with the output circuit of tube 5 leading from plate P through inductance 9 tuned by condenser I0, constituting the primary winding of intermediate frequency transformer H.

In the circuit arrangement for tube 5 as described, three indicators A, B and C serve to locate any defect which may exist in different parts of the circuit, such as in the case of indi cator A, an open resistor R1, a shorted condenser C1, or a. defect in other parts of the circuit; in the case of indicator C, an open resistor R3 will be shown, or a shorted condenser C3 will be indicated; and in the case of indicator B, an open resistor R2 will be indicated, a shorted condenser Cz can be located, or a shorted condenser C4, or an open path in the primary winding 9 of intermediate frequency transformer II will be indicated. relied upon to show the operating condition of tube 5 and will grow dimmer as tube 5 ages. Indicators A, B and C will also show conditions of shorts between the tube electrodes.

The next removable section of the receiving set contains the first intermediate frequency amplifier tube I2 which contains heater [4a and cathode Mb, control grid G, suppressor grid Su, screen grid G5, and anode P. The control g id connects to the secondary winding of intermediate frequency transformer II indicated at I5 in the input circuit of tube I2. Safety indicator lamp D is connected in a series path with the suppressor grid Su and cathode Nb, and in series with bias resistor R4. Condenser C5 provides a by-pass path around safety indicator lamp D and resistor R4. The screen grid circuit leading from electrode Gs includes current limiting resistor R5 and indicator lamp E connected to the high Indicators A, B and C can also be c:

ill

potential lead indicated at 8 as B+. Condenser Cs provides a by-pass around resistor R5. Condenser Cr by-passes safety indicator lamp E in circuit with the plate electrode P through primary winding I6 of the second intermediate frequency transformer II. Primary Winding I1 is suitably tuned by means of condenser I8. The safety indicator lamps D and E serve to indicate a condition of an open resistor R4 or a shorted condenser C5 in the case of safety indicator lamp D and in the case of safety indicator lamp E, an open resistor R5 is indicated or a shorted condenser C6 is at once localized or a condition of short in condenser C7 is shown. Indicator lamps D and E also enable any shorts between tube electrodes to be readily observed or any condition of open circuit in the primary winding I6 of the second intermediate frequency transformer II to be indicated. As tube I'2 ages the safety indicator lamps D and E grow dimmer.

The third replaceable section of the receiver contains a second intermediate frequency amplifier tube which I have indicated generally at I9 as including a heater I 9a and a cathode I91; with a control grid G", a suppressor grid S"u, a screen grid G"s, and a plate electrode P". I provide in circuit with the suppressor grid S"u and cathode I9b, the safety indicator lamp F in a series path with bias resistor Rs. The combination of the safety indicator lamp F and bias resistor R6 is shunted by by-pass condenser Cs. I provide in circuit with the screen grid Gs, a voltage limiting resistor R7 arranged in series with safety indicator lamp G1. Condenser C9 forms a by-pass around the voltage limiting resistor R'z. Condenser C10 provides a by-pass around safety indicator lamp G1. The safety indicator lamp G1 is also disposed in the output circuit of the second intermediate frequency amplifier tube I9 and in series with primary winding of intermediate frequency transformer 2I and connected with the plate P". Primary winding 20 is suitably tuned as indicated at 22. Indicator lamps F and G1 serve to show in the case of indicator lamp F, an open resistor Rs or a shorted condenser Cs; and in the case of safety indicator lamp G1, an open condition of resistor R7 is indicated, a shorted condition of condenser C9 is shown or a shorted condition of condenser C10 is indicated. Safety indicator lamp G1 also shows a condition of open circuit in primary winding 20 of intermediate frequency transformer 2|. As tube I9 ages, indicators F and G1 grow dimmer. The indicator lamps F and G1 also enable any condition of short circuit between the tube electrodes to be promptly detected.

The next replaceable section of the radio receiver is indicated generally as including an elec tron tube 22 connected to function as a diode detector. Tube 22 includes heater 22a, cathode 22b and control grid G' and plate P'. The control grid G' and plate P' are interconnected to serve as one electrode forming the second electrode of the diode with respect to cathode 22b. The output or secondary winding 23 of the intermediate frequency transformer 2|, tuned by means of condenser 24 connects with the diode detector circuit and with the grid circuits of the preceding tubes 5 and I2 through resistor 25 for purposes of automatic volume control. Condenser 26 is provided for filtering the energy supplied to the automatic volume control circuit. I provide the volume control potentiometer 21 in association with resistor 25 as shown and assotube 30.

ciated with filter condenser-28 forming part of thefilter network with condenser 26.

The unit including the automatic volume control circuit just described has been disclosed without the insertion of safety indicator lamp, but it should be understood that safety indicator lamps may be employed. I have found that the parts of the automatic volume control circuit are very substantial in practice and the danger of faults occurring in this portion of the circuit are not as serious as is the situation in other units making up the replaceable sections of the set.

Thenext replaceable unit for the apparatus of my invention is constituted by the first audio frequency amplifier stage indicated-generally as including tube 3!]. Tube 30 contains heater 30a and cathode 30b, control grid G and plate P". The variable tap 29 on resistor 2'! enables the energy at the selected amplitude to be impressed on the audio frequency amplifier stage and control grid G thereof for insuring the impression of energy at desired amplitude on the audio frequency amplifier system. Control grid G is .maintainedat the proper potential for amplification of energyon'the straight portionof the amplification characteristic curve of the .tube through bias resistor 32 connected in series with biascell 3 3. The output circuit of tube 30 includes coupling resistor R8 and condenser C11 associated therewith. Safety :indicator lamp H is disposed in series with coupling resistor Re. Any failure of coupling resistor R8 or *shorting of condenser C11 is at once indicated by safety indicator :lamp H. Moreover, the condition of 'shorts'between tube electrodes in tube .30 may 'be indicated by safety indicator lamp H. As tube 30 ages, the indicator lamp H grows dimmer.

The next unit of the replaceable unit system of the radio receiver contains the second audio frequency amplifier stage constituted by tube 34 containing 'heater34a and cathode 34b, control gridG screengrid G s and aplate electrode P". The tube 34 hasits input circuit coupled through condenser C12 with the output of the first stage of "audio frequency amplification constituted by A bias resistor R9 is arranged for impressingthe required operating potential ongrid G". Bias resistor R9 is connected in circuit with resistor R which connects to ground. A midtap 35 between resistors R9 andRm connects to the negative side of the main filtersystem as indicated at 36. The output circuit from plate P includes the primary Winding 3'! of output transformer-'38 and the safetyin'dicator lamp I to the positive side of the power supply system at 8 and tothe positive terminal 39 of the main filter. A safety lamp J is connected in shunt with resistor R10. The safety lamps I and J indicate respectively an open condition in the primary winding 31 of output transformer 38 'or a condition of short in tone control condenser C13 in the case of safety indicator lamp I or in the case of safety indicator'lamp J an open condition in resistor R10. Indicator lamp I indicates any condition of short-circuit between tube electrodes and will also grow dim as tube 34 ages.

The rectifier and the main filter system are included in an independently replaceable unit. I have shown the elements of the main filter generally asincluding condensers C14 and C15 and the :reactance 40 of the electro-dynamic sound reproducer, whichI haveindicated generally at 45. The main :filter includes safety indicator lamps K and L'connected as shown, in circuit withthe elements of the full-wave rectifier tube 42. Safety indicator lamp K indicates a condition of open circuit in the speaker field 40 or a condition of short in condensers C14 or C15. The condition of illumination of safety indicator lampK also shows any condition of leakage in condensers C14 or C15 or any condition of ageing of rectifier tube 42. Safety indicator lamp L is disposed in the negative lead of the rectifier and provides a further method of indicating the condition of the circuit through the speaker field and the condition of the condensers C14 and C15. .Safety indicator lamp L also protects the filter -elements'in the event of a short within the rectiwinding 44 energized from any suitable alternating current source connected at 45.

The transformer is provided with suitable secondary windings such as the plate supply winding 46 connected with full-wave rectifier tube '42, the

cathode heating winding 41 connected with the cathode of rectifier tube 42 and winding 48 con- ;nectedto supply the heaters .of the several tubes 5, I12, 19, 22, 30 and 34 of the radio receiver.

Throughout the .radio receiver where I have indicated the "safety indicator lamps A, B, C, D,

E, F, GI, -H,.I, J, K and L, I proportion-the filamentary element of each of the lamps for protecting the associated elements against destructive effects of excessive currents while being so proportioned as'to permit the passage of desired normal operating current and also being so proportioned that such normal operating currents will excite the safetyindicatorlamps to acondition of luminosity whereby the several indicator lamps serve as individual assurances that the circuits of the respective units are operating properly and in normal manner. Any safety indicatorlamp whichisnot energized at once gives an indication as to the location'of the defect in the circuit. Inasmuch as the several replaceable .units carrying the safety indicator lamps may be readily replaceable, an entire unit or part thereof is replaced in the circuit upon removal of the defective unit and the set immediately restored'to operative condition with minimum expense and without the skill normally required of a service man in attending the usual type of radioreceiver.

In order to summarize the -functions of the indicator lamps, I .have tabulated the several conditions whichexist, assigning to the several replaceable units .references as 1 follows Unit #l'-'first detector, oscillator, mixer and radio frequency amplifier stage Unit #2''-'first.intermediate frequency amplifier stage Unit #3-sec0nd intermediate frequency amplifierstage Unit #5'.-first audio frequency amplifier stage Unit #6'-.:second audio frequency amplifier stage Unit #'|--rectifier and main power filter lishing and completing the connections through the high frequency circuits of the receiver in ac- The tabulation of the results shown by the indicators in the several units, is as follows:

Unit Indicator Indication Indicator Indication Replace part 1 A B & Bright 01 (short) 1. A B Brightr. 02 (short) 1'. A B & 0 Out R1 (open) 1' A B Out R2 (open) 1 A 0 Bright C: (short) 1' A 0 Out R3 (open) 1. A B Burnt out. 04 (short) 1'. A B Out I. F. T. #1 (open) 1 A Dim B & 0 Dim Tube #5 (weak) 2' D E Bright 0 (short) 2 D E Bright Ct (short) 2. D E Out R4 (open) 2 D E Dim R (open) 2 D E Burnt out 01 (short) 2' D E ut I. F. T. #2 (open) 2 D E Dim" Tube #12 (week) F 6; Bright Cs (short) F Gr Bright 09 (short) F G; Out Rs (open) F G: Dim R1 (open) F G; Burnt out. Cm (short) F G Out I. F. T. #3 (open) F Gr Dim Tube #19 (weak) H r. 011 (short) H r Ra (open) H Tube (weak) I Out J Transformer #38 (open) I Burnt out I 013 (short) I J Bright Rm (open) I .l Dim 012 (short) I Dim J Tube #34 (weak) K Out .i L Out Speaker Field (open) K Burnt out L Burnt out. 014 (short) K Out L Burnt out. 01 (short) K Bright L Bright 014 (leaky) K Dim L Brightnu C15 (leaky) K Dim L Diru Tube #42 (weak) the direction of arrow A in Fig. 3 and in side.

elevation looking in the direction of arrow B in Fig. 4. For convenience, I have shown the equipment mounted on a main base 5|! which supports the heart shown generally at 5 I. The heart may take a variety of forms but in the particular embodiment of my invention as illustrated, the heart extends in a substantially vertical plane and receives the several units in quick detachable and replaceable arrangement by insertion from opposite sides into the heart. In the plan view shown in Fig. 2, the units which appear in cordance with the diagram illustrated in Fig. l. The wave band switch and wave band unit indicated at 59 has provision for the connection of the sets of inductively coupled units indicated at 2 in the wiring diagram at the set of contacts (Fig. 3). The sets of oscillator inductor coils in the diagram in Fig. l, are connected to the unit 59 through sets of contacts indicated at 6| in Fig. 4. The selector switch for the sets of coils 2 and 1 connected respectively through sets of contacts 60 and BI, is controlled through shaft 62 from knob 63 adjacent the volume control and tone control knobs 54 and 5'! respectively.

The sound reproducer 4| illustrated in diagram in Fig. l, is schematically shown in position with respect to the receiving apparatus at 4| in Fig. 2,

the figure are 3', the second intermediate fre- 55 connected through sets of leads 64 with the cirquency amplifier stage; 4, the second detector; cuits of the radio receiving apparatus. The tun- 5, thefirst audio frequency amplifier stage; and ing unit comprising adjustable condensers I 6', the second audio frequency amplifier stage. shown in diagram in Fig. 1, is illustrated in posi- The heart 5| also has engaged therewith the detion with respect to the receiving apparatus in tachable and replaceable volume control unit 52 00 Fig. 2, connected through leads with the wave controlled through shaft member 53 from control change unit 59. knob 54 on one side of the heart. On the other The details of the heart are shown more parside of the heart, the tone control switch unit 55 ticularly in Fig. 5. Referring to Fig. 5, the conmay be engaged or disengaged with respect to struction of the heart will be understood by conthe heart. The tone control unit 55 is controlled sidering these views collectively in superimposed hr suitable h f 56 f m o 5 proiectrelation. The heart is constituted by two lamiing to a control position adjacent knob 54. nations of insulation material indicated in Fig. 5 The wave band switch or frequency control at 66 and 61. The laminations 66 and 61 carry unit is engaged within a recess 58 adjacent one the electrically conductive members forming the end of the heart 5| and is indicated as a unit at combining means for the circuits through the 59. The entire unit 59 is insertable into or removable from the recessed portion 58 of the heart 5| and carries terminal connectors thereon which engage with correspondingly aligned terminal connectors within the heart 5| for estabheart. Insulated plate members 68 and B5 serve as confining supporting and spacing means for the laminations 66 and 61 and for the conductive elements carried thereby. The entire structure of the heart is suitably secured together by means extending through the laminations 'and'is. electrically shielded by means ofia metallic casing represented generally at E9. The conductive elements carried by the laminations 95 and 91 are in the form of short transversely extending metallic tubular members, certain of which are electrically bonded by buses carried by the laminations.

The arrangement of the electrically conductive members on the laminations I56 and 51 is shown more clearly in the perspective view in Fig. from which it will be observed that lamination 55 carries tubular conductive members illustrated at II, I2 and I3, tubular conductive members II and I2 being interconnected by bus I3l; lamination 67 of the heart carries transverse tubular members H9 and Ill interconnected by bus H2 and transversely extending tubular members H9 and H5 interconnected by bus H9; lamination 65 carries short tubular transversely extending members l5, I6 and I1, tubular members 15 and '19 being interconnected by bus I39; lamination El carries tubular member I4 interconnected by bus I IS with tubular member I I1 projecting in a direction opposite to the direction of projection of member M, the member I I! being transversely aligned with member TI; lamination 56 also carries transverse tubular members I8, I9, 89 and BI, tubular members I9 and I9 being interconnected by bus I39; lamination 9'! carries transversely extending members H9 and I29 interconnected by bus I2I and also transverse tubular members I22 and I23 interconnected by bus I29; lamination 51 carries transversely extending tubular members 82 and 83 interconnected by bus I3I; lamination 95 carries tubular members 84 and 85; lamination 65 also carries transversely extending tubular members 85, 99, 99 and 9 I, members 99 and 91 being interconnected by bus I25; lamination 91 carries tubular members 8'! and S8 interconnected by the substantially square plate I25. The tubular members 91 and 88 extend transversely through the entire heart; lamination 51 also carries tubular members I21 and I28 interconnected by bus I29; lamination 99 also carries transversely extending tubular members 95, 95 and 9?; lamination 51 carries transversely extending tubular members 93 and 94 interconnected by plate I26 which pass entirely through the heart. It will be observed that the transversely extending members 92 and 95" also pass wholly through the heart as is the case also with respect to the tubular members 92 and 33 carried by lamination 5i; tubular members 91 and 99 are carried by lamination El; and tubular member 95 is carried by lamination 69; lamination 6! also carries transverse tubular member I23 which is interconnected through bus I29 with tubular member I21; lamination 56 also carries transversely extending tubular members 93, I99 and I9I; lamination 91 carries tubular member 99 and also tubular member I39 connected therewith through bus I5I. Tubular members I99 and I 9| are interconnected through bus I 32; lamination 55 also carries transversely extending members I92 and I93 interconnected by bus I33; a separable connector I39 is arranged to fit within a groove i3 la in. lamination 65 and pass through an aperture I35 in lamination 59 and support a tubular member I95. The opposite end of connector I39 connects to tubular memtubular members I 93 and I09 interconnected by bus I51. The lamination Iili is recessed as indicated at IM to receive the right elbow connector shown at I41.

It will be understood that the tubular conductive members which are carried by lamination 61 project through aligned apertures in lamination 95. I have illustrated, for example, aperture 15a in lamination 65, aligned with conductive member M, supported by lamination 67. Similarly, apertures 82a, 83a, We and 88a in lamination 66 allow for the passage of tubular conductive members 92, 33, 81 and 98 carried by lamination 51. Lamination 95 is apertured at 93a, 94a and 99a for the passage of tubular conductive members 93, 94 and 99 on lamination 51, respectively. Lamination 51 is apertured at 86a, 92a and 95a for the passage of the projecting ends of tubular members 89, 92 and 95, carried by lamination 95. The member interconnecting tubular conductive members 89, 89, 92 and 95 on lamination 66 is shaped as shown at I49. The member interconnecting tubular conductive members 82, 83, 99 and I39 is shaped as represented at I3I and is insulated from interconnecting member I49 by virtue of the fact that it is disposed in a plane spaced from the plane of interconnecting member MII. As has been hereinbefore noted, certain of the tubular members project in opposite directions transversely of the heart while others of the tubular members areselectively arranged so that some of the tubular vmembers project in one direction from the heart while others of the tubular members project in the opposite direction from the heart. The laminations 55 and 61 are recessed in front thereof as represented at 58. The parts of the laminations which interengage are provided with semicylindrical recesses indicated generally at MI in lamination 56 and I42 in lamination 51 which are aligned with each other to receive between them the conductive tubular members I43, I44, These tubular members I 43--I 41 inclusive, are each provided with right angular bends and extend transversely with respect to and away from lamination 6! and through the confining, supporting and spacing plate 69. The tubular members I43I4I inclusive terminate within the recess 58 and receive quick detachable connecting means from the wave change unit 59.

As heretofore noted, tubular members 13 and 89 are interconnected by bus I99; tubular members I1 and 94 are interconnected by bus I99; tubular members 8! and 96 are interconnected by bus I59; and tubular members and 91 are interconnected by bus I5I. The several buses heretofore described are suitably housed within recesses provided in the laminations.

The entire unit as heretofore noted, is contained in the metallic shield or casing 1.9 and care is taken to cut away the metallic shield around each of the connecting means to avoid any possibilities of short-circuit. I have shown the two interior plates 66 and 67 of the heart carrying tubular members aligned with coacting apertures and arranged in cooperation with aligned apertures in the confining, supporting and spacing plates 58 and 99; but it should be understood that plugs instead of tubes may be used interchangeably or other forms of connecting devices may be employed and the tubular members have merely been selected as one illustrative embodiment of my invention.

For convenience, I have tabulated the functions of the transverse connectors carried by the 'larninationsififi 'andfil as follows:

I'I-'I2#plate output (Fig. 32) or voice coil of speaker (Fig. 29). 13tone control. 1'4-'grid input to first audio frequency am- I plifier stage. I5'I6fie'ld return from speaker.

'IJ-tone control. I

18-plate output to second audio frequency amplifier stage.

T9.plate input to second audio frequency amplifier .stage (in common with 18).

Bil-ground to tone control (in common with 13).

8Ioutput from switch to power transformer.

82-"heater input to first audio frequency amplifier stage (82 projecting from lamination 61 through plate 69 serves as the heater input to the second intermediate frequency amplifier stage).

M -heater input in second audio frequency amplifier stage (83 projecting from lamination 61 through plate 69 serves as the heater input to the second detector stage).

='84output to tone control (in common with 11).

85input to switch for alternating current power supply.

86positive B voltage input to first audio frequency amplifier stage (in common 5 with '89, '92 and '95), ('85 projecting from lamination 6'! through plate 69 'serves as the positive B voltage input to the second intermediate frequency amplifier stage).

BrI-ground 'and heater input to first audio frequency amplifier stage.

llll eground and heater input to second 'audio frequency amplifier stage (88 projectingfrom lamination 61 through plate 69 serves as the heater and input to second detector stage).

89-positive B voltage input to second audio frequency amplifier stage (in common w'ithBIiyB'Z and 95) ELM-voice coil of speaker (Fig. 29) or positive B voltage (Fig. 32).

'92-rec'tifier cathode input and positive B voltage output to all stages ('92 pro- 'jec'ting from lamination 66 through E k-ground output to rectifier (94 projecting from lamination Bl through plate '69 serves as the ground and heater input to the first detector stage). 95-cathode output to rectifier (95 projecting from lamination 66 through plate '59 serves as the positive 13 voltage input to the first intermediate frequency amplifier stage).

9Einput from switch to power transformer (in common with BI).

ill-alternating current power supply input to switch.

98-center tap input to rectifier.

SIB-heater output to tubes (99 carried by lamination 6'! and projecting therefrom through plate 69 serves as the input to the first detector stage).

IOU-I0 I-alternating current input to power transformer.

I fl2-cathode input to rectifier.

|03cathode output to rectifier.

IM-center tap output to rectifier and speaker field.

IDS-input to speaker field.

ID6high voltage input to rectifier.

HIT-high voltage output to rectifier.

I IJ8high voltage input to rectifier.

IDS-high voltage output to rectifier.

I IOoutput to second detector.

I I I--input to second detector.

'I I I-output to volume control.

I I5input to volume control.

II1grid input to first audio frequency amplifier stage.

I Iii-output to second detector.

I2Ilinput to second detector.

I22-l 23ground to volume control.

I21.A. V. C. output to second detector. I 28-A. V. C. input to first detector. I30heater input to first intermediate frequency amplifier stage.

The detachable tuning unit indicated generally in Fig. 2 is shown schematically in difierent embodiments in Figs. 6 and 7. In Fig. 6 I have shown the manner of mounting the frame I52 of the tuning unit which includes condensers I controlled by adjustable shaft operated from knob [53. The frame I52 of the condenser carries a socket member I54 supporting pin-like contacts I55 in insulated relation and electrically connected with the tuning condenser units I and also electrically connected with indicator lights for illuminating the indicator dial if desired. The entire tuning unit may be readily inserted into or removed from a suitable receptacle providing means for both mechanically supporting the tuning unit and establishing electrical connection therewith.

In lieu of the electrical connections through the sets of pins I55, I may mount the tuning unit directly upon legs as represented at I56 in Fig. '7 which are insertable into or removable from a suitable socket mounting, but in which the legs I56 do not perform the function of completing electrical circuit connections. In this arrangement the fiexibleleads indicated at 65, connect the tuning unit with the wave change unit 59 as shown diagrammatically in Fig. 2.

The details of the first detector, oscillator, mixer and radio frequency amplifier stage heretofore designated at I are set forth more clearly in Figs. 8, 9, 10, 11 and 12. In order to make clear the structure of each of the units, I have shown each of the units in plan view with parts fiattened out to illustrate the relation of the elements. For example, in Fig. 8, the chassis of insulation material for unit I' is designated generally at I51 with the sides thereof folded outwardly. Chassis I51 serves as insulated mounting means for buses of minimum length which are secured to the insulation material comprising the chassis I57 in proper position for mechanically mounting the resistor and condenser units and establishing a connection with the plug connectors which interengage with the tubular mem- 

